Cardiac glycosides such as digoxin and digitoxin and sympathomimetic drugs are traditionally used for the treatment of congestive cardiomyopathy and cardiac insufficiency. The cardiac glycosides have, however, distinct toxic side effects and only a narrow therapeutic range while the sympathomimetic drugs show undesirable chronotropic and arrythmogenic side effects and are ineffective when taken orally.
This situation has led in recent years to the development of new, positively inotropic substances, of which amrinone (J. R. Benotti et al., N. Engl. J. Med. 299, 1373 (1978) and milrinone (A. A. Alousi et al., J. Cardiovasc. Pharmacol 5, 792 (1983) are examples.
These substances, however, have an undesirable spectrum of side effects when administered orally so that their use has been restricted to other forms of administration.
It was therefore an object of the present invention to provide new, more effective positively inotropic substances with an improved therapeutic profile.
This problem is solved by the present invention.